1. Field of the Invention
The present invention relates to a cleaning device in an image reproducing apparatus using magnetic toner and whereby toner remaining on an image pattern support may be removed, transported and recovered.
2. Description of the Prior Art
In such an electrophotographic copying apparatus and facsimile apparatus which are typified of an image reproducing apparatus, an image recording has been performed in such a manner that an electrostatic latent image of a document or an electric information is formed on a photosensitive receptor or a dielectric by applying a reflected light or an electric information signal which has been obtained by exposing and scanning the original document, said electrostatic latent image thus formed has been visualized by a development process, the visualized image has been then transferred onto a copy paper, and transferred image on the copy paper has thus been fixed.
FIG. 1 shows a schematic construction of a conventional type electrophotographic copying apparatus, wherein a lamp 2 irradiates light to a document G placed on original document table 1 which reciprocates in the direction of the arrow shown by the solid line, and the reflected light from the document G is projected onto a photosensitive receptor 3a of a rotatable drum 3 rotating in the direction of the arrow, and thus, an electrostatic latent image of the document G is formed on photosensitive receptor 3a. There are arranged around rotatable drum 3 with a charging electrode 4 for charging photosensitive receptor 3a, a developing device 5, a transferring electrode 6, a separating electrode 7, a charge eliminating electrode 8 and a cleaning device 9 of a fur brush type, one after another. The electrostatic latent image thus formed is visualized by developing device 5, and the visible image thus obtained is transferred by transferring electrode 6 onto a copy paper P having been fed from such a paper feeding device 10 such as a paper cassette by means of a transporting device 11. After transferring, copy paper P is separated from photosensitive receptor 3a by separating electrode 7 and is then transported to fixing device 13 by transporting device 12, and therein is fixed, and is thus ejected to copied paper ejecting tray 14.
In the abovementioned apparatus, and in order to use photosensitive receptor 3a repeatedly, it is required to eliminate a residual electric charge and toner which are still remaining on the surface of photosensitive receptor 3a after the transferring process in a series of the abovementioned electrophotographic processes, and to cope therewith, such the residual charge is eliminated by charge eliminating electrode 8 and such residual toner are removed by cleaning device 9, respectively.
As for the cleaning devices to be used in the image reproducing apparatuses of this kind, there have been known various ones such as those of the fur-brush type, blade type, magnetic brush type and the like. In a fur-brush type cleaning device, a fur-brush made of animal hairs such as rabbit fur or of synthetic fibers is continuously rotated to remove the toners remaining on the surface of a photosensitive receptor, and the toners adhered to the fur-brush are flicked off by a toner flicking plate that is the so-called a flicker-bar, and the toners thus flicked off are vacuum-absorbed or are absorbed by a fan to recover them through a filter. In a blade type one, a blade made of an elastic synthetic resin is brought into pressure contact with the surface of a photosensitive receptor to remove remaining toners. In a magnetic-brush type one, lastly, which is exclusively used with magnetic toners, a non-magnetic cylindrical sleeve is provided closely to the surface of a photosensitive receptor so that magnets of which poles are opposite each other are alternately arranged respectively inside the sleeve, and the sleeve is rotated with carriers being adsorbed thereon or the magnets are rotated, to adsorb the remaining toners on the surface of the photosensitive receptor and then to remove the remaining toners, and thus, the toners are scraped off by a blade or the like from the surface of the sleeve to recover the toners.
In recent years, with the advance of the copying apparatuses in which the copying speeds are being increased and the moving speed of the photosensitive receptors are accelerated, a blade type cleaning device cannot sometimes afford to clean up toners satisfactorily, and therefore, fur-brush type ones have so far been utilized in high-speed copying apparatuses. Such a fur-brush type cleaning device is characterized in that it does not damage the surface of a selenium photosensitive receptor drum as a blade does, because the fur-brush does not press itself against the surface of the drum and does not have such a blade to which a solid matter may adhere, and therefore it is possible to extend the life-time of the photosensitive receptor. From the points of view mentioned above, a fur-brush type cleaning device has attracted special attention recently.
FIG. 2 shows a schematic construction of a magnetic-brush type cleaning device having so far been used. Wherein, reference numeral 9 indicates a cleaning device in which there are arranged inside housing 91 with fur-brush unit 92, magnetically toner recovery-unit 93 and scraping-off blade 94 among those of which said fur-brush unit 92 is provided so as to rotate coming into contact with photosensitive receptor 3a, said magnetically toner recovery unit 93 and said blade 94 are provided closely to the fur-brush unit 92 respectively. Fur-brush unit 92 comprises that implanted brush-fiber 92b made of animal hairs or synthetic fibers in on the circumferential surface of brush-core 92a and, on the other hand, the tip of protrusion 91a formed inside housing 91 is extended to the position where the tip gets in touch with brush-fiber 92b. Magnetic recovery-unit 93 is so designed that, magnet-roll 93b formed by arranging alternately the poles being opposite to each other inside non-magnetic cylindrical sleeve 93a, the magnet-roll 93b is so arranged as to keep a very narrow gap from the internal surface of cylindrical sleeve 93a which is rotatable in the direction of the arrow. Scraping-off blade 94 is so provided as to come closely into contact with the surface of cylindrical sleeve 93a.
Now, in the abovementioned cleaning device, when fur-brush 92 and cylindrical sleeve 93a are rotated respectively in the direction of the arrow, magnetic toners T remaining on photosensitive receptor 3a are electrostatically attracted by the frictional charge of brush-fiber 92b to remove from photosensitive receptor 3a. The magnetic toners adhered to brush-fiber 92b are knocked off by protrusion 91a of housing 91 and are then attracted and transported onto cylindrical sleeve 93a by the magnetic attraction force of magnet-roll 93b. Toners on cylindrical sleeve 93a are scraped off by scraping-off blade 94 to be stored in reservoir 91e provided in a portion of housing 91.
However, if scraping-off blade 94 is increased in its contact capability with cylindrical sleeve 93a in order to improve the toner recovery, the adjustment of such contact capability would relatively be difficult because the loads would be increased to cylindrical sleeve 93a and at the same time the toners are also given stresses. In the case of utilizing toners thus scraped off, an additional means for transporting toners to a development device is required. Besides the above, the fur-brush type cleaning devices would be unsuitable for recovering toners unless some countermeasure could be taken to prevent the toners from mixing in with the brush-fiber chips of a fur-brush having been worn out for a long time usage, though it could probably be suitable if some measure also could be taken. There might further cause such a problem that the inside of the housing is apt to be contaminated with toners being blown up smogwise when the fur-brush and the cylindrical sleeve are rotated at high speed.